Project Summary/Abstract: The emerging field of optogenetics ? using light to engage biological systems ? holds tremendous promise for dissection of neural circuits, cellular signaling and manipulating neurophysiological systems in awake, behaving animals. However, the technological limits for implementing optogenetics in dissecting neuromodulators in awake, freely-moving behavior is clear while working with paradigms that require discrete spatiotemporal control of receptor signaling and when investigating neural circuits that have very small diverse, ?hard to reach? architecture, such as heterogeneous brain nuclei. To engage neuropharmacological receptor substrates, neuroscientists in nearly every field use cannulas (simple metal tubes) and have more recently adopted tethered fiber optics for in vivo optogenetics to control local release of neuromodulator monoamine or neuropeptides. Unfortunately, these current methods are rather limited and difficult to implement because they severely limit the spatiotemporal control over receptor signaling pathways in discrete cell types. Moreover, current technology lacks a full tool box for multiplexed, subcellular, spatiotemporal control of G protein coupled receptor signaling, the predominant means for neuromodulator communication in the brain. For these reasons, an innovative effort combining neuroscience with biochemistry and pharmacology was necessary in order to bring spatial-temporal in vitro and in vivo control over GPCR- neuromodulator signaling. Therefore, here we directly address the central goals of this RFA-NS-16-775 in the following manner. The central goal of this proposal is to develop a cutting-edge v2.0 Opto-XR receptors that spatially and temporally control neuromodulator signaling in vitro and in freely moving animals. We have proposed an uniquely integrated approach to achieve this goal that brings pharmacologists, physiologists, biochemists, and neuroscientists together in a unique parallel manner. In the two specific aims we will develop and test these novel tools in vitro and in vivo: 1) To develop mutant Gi and Gs, Opto-XR v2.0 receptors with greater signaling dynamics and altered color spectra and sensitivity using structure-function analyses and thorough in vitro characterization; and 2) To develop utility and characterize Gi and Gs versions of Opto-XR v2.0 constructs in vivo and in models of freely-moving behavior using both traditional and wireless optogenetic approaches. Successful completion of the proposal will provide the wider community of neuroscience with a long awaited spatiotemporal manipulation of GPCRs ? neuromodulator signaling within neural circuits in awake freely behaving animals. This new technology will also further widen the field for approaches that are capable of discrete control and optodynamic simulation of neuromodulator function in brain tissue.